Box Shaped Heart

I've got a couple of dozen songs I've written, some of which I can play and some of which I fear are too advanced for my current learning curve on the guitar. (This is the songwriting equivalent, I guess, of buying a pair of jeans too small for you to encourage yourself to diet into them).

Worry not, I shan't swamp you by posting ten at once. Here's one which I think is fairly typical of my style and level of compositional skill, but which I think definitely needs some tweaks. Feedback, therefore, welcome:

BOX SHAPED HEART

Cruising the streets with nothing much in mind
And an hour or two to kill
Got a carrot in front, and a stick up my behind
It's a triumph of lack of will.
I could fly to the stars or take a rocket to Mars
But I'd sooner just stay in bed
Cos since you left me, it's so easy to see
That I haven't got a thought in my head,

And I've got an empty box
Right here in my chest
An empty box
Right here in my vest
I should pull up my socks
And behave like the rest
But I just can't play that part
Got a box shaped heart.

I don't want you to think I'm angry at you
Or I've got revenge on my mind
But since you told me that our loving was through
I've no energy that I can find.
So I wander around with my feet on the ground
And my head miles up in the sky
Or I lie on the sofa watching Gordon the Gopher
While my mind replays your bye-bye

And I've got an empty box
Where my heart used to be
An empty box
And you did it to me
You're as smart as a fox
I'm as dumb as a tree
And I should have known from the start
Got a box shaped heart.

Got a brownout of energy, pleading for clemency,
Fearful in symmetry, excess of lethargy –

Now I don't really care if you live or you die
And the same thing goes for me too
I really should hate you but it's one more thing I
Just don't have the willpower to do.
Now you're far away with your catch of the day
And I'm sure that you're having a ball
Though I know I've been had I'm too tired to be mad
In fact I can't feel bugger all

Cos I've got an empty box
Where my heart used to be
An empty box
And you did it to me
You're as smart as a fox
I'm as dumb as a tree
And I should have known from the start,

Got an empty box
Right here in my chest
An empty box
Right here in my vest
I should pull up my socks
And behave like the rest
But I just can't play that part
Got a box shaped heart.